Chapter 14

Technology in urology,principles of uroradiology andmiscellaneousJohn A Bycroft and Jim AdsheadEndourology technologyQ. What are the characteristics of the ‘ideal’ stent?A. The ideal stent would have the following characteristics:1

• good memory, with a configuration that prevents migration• excellent flow characteristics• radio-opaque• biologically inert (biocompatible)• resists biofilm formation, encrustation and infection• made of a flexible material with a high tensile strength• easy to insert• easy to remove or exchange• reasonable price• minimal complications.Q. What are the indications for stent insertion?A. The indications can be divided into two categories – elective and emergency.Elective indications include the following:• protection of anastomosis (pyeloplasty, ureteric reimplantation)• to overcome extrinsic ureteric compression• prior to chemotherapy to optimise renal function in obstructive uropathy• pre-operatively (in gynaecological or colorectal surgery) to aid identificationof the ureter.Emergency indications include the following:• relief of ureteric obstruction• management of ureteric trauma.Q. What are the complications of ureteric stent placement?A. In addition to the complications of actual insertion, these can be divided intocommon and rare complications, as shown in Table 14.1.Viva practice for the FRCS(Urol) examination326Table 14.1 Common and rare problems associated with ureteric stent placementCommon problems Rare problemsTrigonal irritation ObstructionHaematuria KinkingFever Ureteric injury/ureteric perforationInfection Stent misplacementInflammation Stent migrationEncrustation ‘Missed’/forgotten stentBiofilm formation Tissue hyperplasiaQ. What are ureteric stents made of? Why are they radio-opaque?A. Ureteric stents are manufactured from a variety of polymers, such as polyurethaneand styrene-ethylene-butylene (C-flex). The radio-opacity of stents isincreased by coating them with metals such as bismuth and barium.Silicone stents are also manufactured. These are stiffer and therefore maycause more mucosal irritation, but can be left in situ for up to 1 year (in contrastto conventional polyurethane stents, which need to be changed every 6 months)

Stents are generally 22–30 cm in length and are usually of the ‘double-pigtail’variety. Sizes are generally in the range 4.7–8.0 Fr.Metallic ureteric stents are increasingly being used for malignant uretericstrictures, e.g. the Memokath™ ureteric stent, which is made of nickel-titaniummemory-shape alloy (Nitinol).Q. What are the different types of ureteric guidewires available?A. Many forms of ureteric guidewires have evolved over the years. Most guidewiresare of the order of 0.035–0.038 inches in diameter, and approximately 150 cmlong. Various configurations exist, and wires are commonly coated with PTFE(polytetrafluoroethylene) and have flexible tips of various lengths. Variationsinclude hydrophilic wires (such as the Terumo wire), guidewires with a hydrophilictip (e.g. the Sensor wire) and stiff wires (e.g. the Amplatz Super Stiff).Q. What are the various baskets available for ureteroscopic surgery?A. A large number of ureteroscopic baskets are commercially available. Theymay be either ‘tipped’ or ‘flat wire’, as used in semi-rigid ureteroscopy, or ‘tipless’,as used in flexible ureterorenoscopy. The tipless variety may allow easieraccess using the flexible scope, and avoid trauma to the collecting system (easilyinserted into the renal calyx if necessary). Baskets are commonly made ofnickel-titanium memory-shape alloy (Nitinol), and range in size from about 2 Frto 3.2 Fr. Baskets are available that open in different ways (e.g. ‘parachute’ and‘helical’).Q. Describe how a modern telescope, as used in cystoscopy, works.A. Originally, before the work of Professor Harold Hopkins, telescopes consisted offine lenses cemented into long metal cylinders separated by long air spaces. Thatsystem was replaced by the Hopkins rod–lens system in the 1950s. This system,which is still in place today, essentially consists of a series of long glass rods ina metal cylinder separated by ‘lenses’ of air. Therefore internally it is a series ofrelatively long glass rods separated by air, as opposed to small lenses separatedTechnology in urology, principles of uroradiology and miscellaneous327by long air spaces. The advantages of this include durability, superior light passageand image quality, reduced diameter of the instrument (permitting parallelaccess channels), colour reproduction, and the ability to ‘document’ images withphotography or video.Light is transmitted by optic-fibre bundles running from an external lightsource (note that this is usually a halogen external light source, which emits ‘yellowish’light – thus the need for white balancing; neon light sources are expensivebut do not require white balancing).Q. How does an optic fibre work? What are the two main applications of opticfibres in urology and how do they differ?A. Optic fibres are flexible glass (or plastic) fibres that allow light to pass throughthem via a process termed total internal reflection. Optic fibres are groupedtogether in a parallel fashion and protected by external plastic sleeves.They have two main uses in urology:• Transmission of a light source. ‘Light leads’ transmit light from an externalsource to endoscopes. These leads consist of non-coherent fibres, and are relativelyinexpensive to produce.• Transmission of images. Image transmission (e.g. from a camera) relies uponcoherent bundles of optic fibres. In this case, the orientation of the fibres at theproximal end must be the same as the orientation at the distal end to preventimage distortion.Q. How is the size/diameter of surgical instruments (e.g. cystoscopes, catheters,

etc.) expressed?A. The ‘French gauge’ (Fr) is used. This was developed by Charrière in the nineteenthcentury. The French gauge corresponds to three times the diameter (inmm). For example, a 21 Fr cystoscope sheath has an external diameter of 7 mm.Q. What are the approximate lengths, diameters and working channel configurationsof the major endo-urological instruments?A. Semi-rigid ureteroscopes. These vary in size depending on the manufacturer andthe working channel configuration. It should be remembered that they use fibreoptics for image transmission, rather than the rod–lens system of traditionalrigid instruments, and therefore have a relatively small diameter that usuallyobviates the need for formal ureteric dilatation. The working element is of theorder of 34 cm long, with the tip approximately 7–10 Fr (i.e. about 3 mm indiameter). If one working channel is present it is usually about 3.4 Fr, whereas iftwo are present they are about 2.3 Fr each.Flexible ureteroscopes (ureterorenoscopes). The configurations vary depending onthe age and model of the instrument. The distal end of the instrument is lessthan 9 Fr, and modern instruments may be even smaller (5.4 Fr, i.e. < 2 mmin diameter). Lengths vary, but are usually around 70–80 cm. Working channelsare approximately 3.6 Fr, permitting the passage of instruments such asbiopsy forceps up to 3 Fr and laser fibres. The endoscope may be inserted bymeans of a hydrophilic access sheath placed over a guidewire. These sheaths areapproximately 45 cm and 10–14 Fr. They may have dual lumens to permit parallelinstrument passage.Viva practice for the FRCS(Urol) examination328Cystoscopes. Adult cystoscope sheaths are generally in the range 17–25 Fr, andapproximately 30 cm long. The components of the cystoscope are the telescope(rod–lens), bridge, obturator and sheath. The telescopes themselves are angledfor various procedures, and are generally 0 degree (for urethrotomy, etc), 30degree and 70 degree (for cystoscopy). Telescopes are colour coded with bandsaround the light-lead connector (e.g. green, red and yellow for 0, 30 and 70degree, respectively).Resectoscopes. These again vary in size depending on the manufacturer and theconfiguration. Common external sheath diameters are 26 Fr and 28 Fr.Sterilisation and disinfectionQ. What is the difference between sterilisation, disinfection and cleaning?A. Sterilisation is defined as the complete destruction of living organisms (includingspores and viruses). This differs from disinfection, which is a process that isused to remove most viable organisms, but which does not necessarily inactivatesome viruses and bacterial spores. Cleaning is a process that physically removescontamination but does not necessarily destroy microorganisms.Q. How is autoclaving performed?A. Autoclaving is a process that combines heat and pressure to sterilise instruments.By combining pressure with heat the temperatures of liquids such as water maybe raised above their usual boiling points to facilitate the process. The autoclaveis thus a form of ‘pressure cooker.’ The three variables used in autoclaving aretherefore pressure, temperature and time. Typical cycles include 134؛ Celsius fora ‘hold time’ of 3 minutes, and 121؛ Celsius for a ‘hold time’ of 15 minutes. Theactual timing of the whole process is longer than these values, of course, as themachines need to safely heat up and cool down.Q. How is disinfection carried out?A. Flexible instruments (e.g. flexible cystoscope) would generally be unable to withstandthe conditions of autoclaving. They are therefore processed by high-level

disinfection. They are manually cleaned with brushes and detergent, and thendisinfected in an automated manner. Ultrasound is used in some devices to facilitatethe cleaning process. Automated machines use a cycle whereby the flexibleendoscope is disinfected with solutions of a chemical such as chlorine dioxide(‘Tristel’).Q. How would you determine the level of disinfection required for reusablemedical instruments?A. These instruments are divided into three classes according to the Spaulding classification,namely critical, semi-critical and non-critical.• Critical instruments are those that penetrate normally sterile tissue (i.e. surgicalinstruments). They generally require sterilisation before and after use.• Semi-critical instruments are those that come into contact with mucousmembranes or non-intact skin (e.g. cystoscopes).• Non-critical items are those that only come into contact with intact skin (e.g.blood pressure cuffs).Technology in urology, principles of uroradiology and miscellaneous329Q. What would you use for scrubbing and skin preparation prior to surgery?A. • Scrubbing:– 4% chlorhexidine (Hydrex)– 7.5% povidone–iodine (Betadine or Videne).• Skin preparation:– inguinoscrotal: 10% aqueous povidone–iodine (Betadine or Videne)– genital: chlorhexidine 0.015% cetrimide 0.15% (Travasept solution).Q. What are the ideal climate conditions for an operating theatre?A. 21؛ C and 55% relative humidity.DiathermyQ. What does Figure 14.1 show?Figure 14.1A. This is an image of a diathermy machine.Q. What is diathermy?A. It is the passage of high-frequency alternating current, in the range 400 kHz to10 MHz, through body tissue. Where the current is concentrated, a temperatureof up to 1000؛ C is produced, allowing the cutting or coagulation of tissue.2

Nerves and muscles are not stimulated with such a high-frequency alternatingcurrent (400 kHz to 10 MHz), as there is no time for the cell membranes ofnerve and muscle to become depolarised (they are stimulated at lower frequenciesonly).Q. What type of diathermy do you use in theatre, and how does it work?A. The main types of diathermy used in an operating theatre are monopolar andbipolar.Monopolar diathermy involves the delivery of high-frequency current froma diathermy generator to the active electrode (diathermy forceps or standardresectoscope loop or ball). High current density at the active electrode, whichhas a small surface area, results in heat at the point of contact with tissue.Current density then spreads from this point, throughout the body, returningViva practice for the FRCS(Urol) examination330to the diathermy generator via the patient electrode plate (earth plate), which isthe diathermy pad placed on the patient. Low current density at this electrodeplate, due to its large surface area (70–150 cm²), results in no heat formation.Importantly, the patient electrode plate should be over a well-vascularised areaaway from any prosthesis, and the underlying skin should be free of scarring orhair to allow good contact of the plate with the patient.With bipolar diathermy, current passes down one limb of forceps (active electrode)

and back to the diathermy generator via the other limb (patient electrodeplate). The advantage of bipolar diathermy is that there is no need for a plate tobe placed on the patient. The disadvantages are that there is no cutting facility,the forceps need to be kept apart, and there is less power.Q. What is the difference between cutting and coagulation?A. The differences are listed in Table 14.2 and Figure 14.2.Table 14.2 Differences between cutting and coagulationCutting CoagulationContinuous output (sine wave)100% on0% off(see Figure 14.2)Pulsed output (interrupted sine wave)6% on94% off(see Figure 14.2)Low voltage High voltageNon-contact mode: vaporisation and cuttingContact mode: dessication (coagulum)Non-contact mode: fulgurationContact mode: dessicationIntense heat (1000؛ C)Charring/spread: lowLess heatCharring/spread: highPower 125–250 W Power 10–75 WTypical diathermy machine setting:150–160Typical diathermy machine setting:40–70Note: The ‘blend’ facility only works in cutting mode – pulsed output (50% on and 50% off).Cutting waveformContinuous output (Sine wave)100% on0% offCoagulation waveformPulsed output (interrupted Sine wave)6% on94% offFigure 14.2 Cutting and coagulation waveforms.Technology in urology, principles of uroradiology and miscellaneous331Q. What are the potential complications and precautions with regard todiathermy?A. The complications and precautions are as follows:• Burns:– due to misapplication of the patient electrode plate– metal prosthesis or implants should not be touched directly with the activeelectrode or the patient electrode plate– use of inflammable preparatory solution may result in superficial burnson skin or in cavities.• Explosions:– in obstructed hollow viscera– if inflammable volatile anaesthetic agents (e.g. ether) are used.• High-voltage electrocution:– of the patient or the surgeon because of faulty cables.• Obturator kick.• End artery necrosis:– especially with monopolar diathermy, during penile surgery.

• Pacemakers:– diathermy needs to be used with caution in patients with pacemakers (seebelow).Q. How are diathermy burns avoided?A. Inflammable liquids (e.g. those containing alcohol) should be avoided. Thepatient electrode plate should be at least 70 cm2 in size, and placed appropriately(see above). The patient should not be in contact with any other metal objects(e.g. drip stands). In addition, touching other instruments with the diathermyprobe (either inadvertently or deliberately) should be avoided (to prevent directcoupling).Q. You are in the middle of a TURP when the diathermy stops working. Howwould you resolve the situation in order to complete the procedure?A. I would perform a series of checks, as follows:1. Make sure that the machine has not been switched off inadvertently.2. Check that the diathermy cable is still connected to the diathermy machine.3. Ensure that the diathermy cable has not broken.4. Make sure that the diathermy cable is properly connected to the workingelement of the resectoscope.5. Ensure that the loop is not broken.6. Check that the irrigating fluid is still glycine (1.5%).7. Make sure that the patient electrode plate is appropriately attached to thepatient and that the return cable to the diathermy machine is still connected.Q. You are contacted by your junior colleague about a 78-year-old patientwho is due to have a TURP in 2 weeks’ time. The doctor suspects that thepatient has a pacemaker, and wishes to seek advice. What are the potentialrisks?A. The main risks with pacemakers and implantable cardioverter defibrillators(ICDs) are pacemaker inhibition, phantom reprogramming and ventricularfibrillation.Viva practice for the FRCS(Urol) examination332• Pacemaker inhibition: the high frequency of the diathermy current may simulatecardiac electrical activity, thus inhibiting the pacemaker. If the patient ispacemaker-dependent, the heart may stop beating.• Phantom reprogramming: the high frequency of the diathermy current maysimulate the radio-frequency impulse by which pacemakers are reprogrammed.As a result, the pacemaker may start to work in an entirely differentmode.Q. What precautions should be taken before, during and after the operation?A. All information about the pacemaker/ICD should be available, including thetype of device (pacemaker/ICD), serial numbers, the date of implantation, thehospital that implanted the device, the indication for the device, and the date andresult of the last check. The patient should have a card displaying this information.The cardiac clinic should be contacted to determine the precise indicationfor the device, and to determine whether the device is due for replacement.In general, diathermy should be avoided in the first instance in such patients,and an alternative treatment strategy should be considered. If the surgical procedureis deemed unavoidable, the following points should be considered.Prior to the surgery, carefully consult the cardiologist, pacemaker clinic andcardiac technician in elective cases (see above). Most devices will not need to beadjusted pre-operatively. However, advice should still be sought, as the consequencesmay otherwise be life-threatening. ICDs are generally set to ‘monitoronly’ to prevent inadvertent activation, and should of course be switched back

after the operation. Consider whether the procedure can be performed withbipolar diathermy (e.g. TURP).During the procedure, the patient plate electrode should be sited so thatthe current path does not pass right through the pacemaker. Furthermore, it isimportant to ensure that it is properly applied. Avoid inappropriate groundingthrough ECG leads. The diathermy machine should be positioned well awayfrom the pacemaker (> 15 cm). The patient’s heart rate should be continuouslymonitored, and a defibrillator should be immediately available, as well as anexternal pacemaker. Surgically, short bursts of diathermy should be used andthe operative time should be short as possible. Antibiotic prophylaxis should begiven, and fluid overload should be avoided in these cases.Clinical magnets may be secured over ICDs to prevent inadvertent shocksand to allow pacemakers to function at a fixed rate. However, they are very rarelyused in current practice, because of the risk of phantom reprogramming.In emergency situations, pre-operative checks may not be possible. However,the device should be checked post-operatively as soon as is practicable.3

Extracorporeal shock-wave lithotripsy (ESWL)Q. Describe the various components of the shock-wave lithotripter.A. Whatever the device that is used, the lithotripter will have four main components.These are an energy source, a medium for transmission of energy (e.g. water),a focusing device and an imaging modality.The first machines to be used were the Dornier lithotripters. These usedelectrohydraulic energy to perform electrohydraulic lithotripsy (EHL), wherebyTechnology in urology, principles of uroradiology and miscellaneous333a spark is produced between two electrodes under water, which results in therapid expansion and collapse of a gas bubble and subsequent energy transmission.A metal hemi-ellipsoid reflector is used to focus the energy. This modalityproduces the most effective shocks, but can be painful, and the intensity of theshock wave is variable. An example of such a machine that is used today would bethe Dornier lithotripter S II.A second type is the electromagnetic lithotripter. This relies on a cylindricalelectromagnetic source, and energy is focused by an acoustic lens. An example ofthis would be the Storz Modulith SLX-F2.Thirdly, piezoelectric technology may be used to produce the energy.Piezoelectric materials consist of ceramic or crystal elements that produce anelectrical discharge under stress or tension (the direct effect). Energy transmissionin this lithotripter relies on the ‘converse piezoelectric effect’, wherebyenergy is produced via the movement of the source when electricity is passedthrough it. An example of a piezoelectric lithotripter would be the EDAP LT02.The acoustic shock wave that is produced has two main phases. First, a shortpositive phase causes erosion at the entry and exit points of the calculus. The stonealso shatters internally due to the compressive effect of the wave. The effectof compression/tension-induced cracks is sometimes referred to as ‘spallation’.Secondly, a longer negative pressure phase component of the wave results in theformation of microbubbles, and the collapse of these microbubbles causes furthererosion of the stone surface via the formation of ‘microjets’. The two phasesare illustrated schematically in Figure 14.3.PressureTime0Figure 14.3 The two phases of a shock wave (shock-wave pressure profile).Viva practice for the FRCS(Urol) examination334Q. What are the indications for ESWL?

A. The indications are as follows:• renal pelvis stones < 20 mm• lower pole stones < 10 mm• upper ureteric stones < 10 mm• sandwich therapy in conjunction with percutaneous nephrolithotomy(PCNL).Q. What are the contraindications to ESWL?A. The contraindications can be divided into absolute and relative.• Absolute contraindications include the following:• uncorrected coagulopathy• sepsis or active UTI• distal obstruction• pregnancy.Relative contraindications include the following:• hard stones (cystine or calcium oxalate monohydrate)• morbid obesity (> 135 kg)• abdominal aortic aneurysm• abdominal pacemaker.Q. How would you consent a patient for ESWL?A. Informed consent for ESWL would involve a description of the procedure, discussionof the alternative treatments, and an explanation of the potential complications.4

Common complications• Haematuria.• Renal/ureteric colic.• UTI requiring antibiotic treatment.Occasional complications• Stones will not break because they are too hard, so an alternative treatmentis required.• Repeated ESWL treatments may be required.• Recurrence of stones.Rare complications• Perinephric haematoma.• Steinstrasse.• Severe infection that requires intravenous antibiotics with or withoutnephrostomy.• Adjacent organ damage (in patients with diabetes).• Hypertension.• Arrhythmias.Intracorporeal energy formsQ. A 53-year-old man who has an 8 mm mid-ureteric stone and JJ stent in situpresents for ureteroscopy. Can you tell me what you would use to fragmentthis ureteric stone?Technology in urology, principles of uroradiology and miscellaneous335A. I would use a lithoclast. The lithoclast is known as a contact-type intracorporeallithotripter. The device allows pneumatically generated energy to be deliveredas kinetic energy to the stone. Compressed air delivered from an external supplyfires a projectile in the handpiece of the lithoclast into a probe (similar to ajackhammer), and the energy is thus transmitted to the calculus (the probe mustbe in contact with the stone to fragment it). The probe tends to ‘bounce’ off thewall of the ureter, minimising trauma, and is considered a safe modality in theureter, although ureteric perforation may still occur if it is used without care. Adisadvantage of the device is that the stone may be retrogradely propelled higher

up the ureter or into the kidney.Lithoclast energy is delivered by a rigid probe, and this therefore limits its useto rigid endoscopes. In addition to fragmentation of ureteric stones, the lithoclastcan be used to fragment renal stones during percutaneous nephrolithotomy(PCNL). (During PCNL the lithoclast can be combined with the hollowultrasound probe, which is able to suck up stone fragments, e.g. as in the SwissLithoClast Master.)Q. What alternative forms of energy could you use for a ureteric stone?A. An alternative modality to the lithoclast in the ureter would be laser, such as the holmiumlaser. LASER is an acronym for Light Amplification by Stimulated Emissionof Radiation. The three characteristics of laser light are its coherence (the lightis parallel), its monochromacity (the light is all of the same wavelength) and thefact that it is in phase (Collimation). Laser is formed by applying energy to a lasingmedium, a process that is known as ‘pumping.’ The energy may be light, chemicalor even another laser, and the medium may be a solid, liquid or gas. The laser chamberitself is fully reflective apart from an aperture that is able to let light escape whenit reaches a certain intensity. Photons are released from the medium when energyis applied, and this in turn leads to the release of more photons from the medium.The light is therefore amplified, and a state known as ‘population inversion’ occurswhereby more light is released than is absorbed. The wavelength of holmium laser is2140 nm, and it is therefore invisible. A secondary red aiming beam is utilised. Thedepth of penetration is 0.4 mm (holmium laser). Laser works primarily via a photoexcitation/photothermal effect (i.e. heat production). Different fibres sizes exist. It isrecommended that 200-μm fibres should be used with the flexible ureterorenoscopeand 365-μm fibres (or less) with the semi-rigid ureteroscope.Electrohydraulic lithotripsy (EHL) should be avoided in the ureter due to the risk ofureteric damage (although it may be used in the bladder). Similarly, the use of ultrasonicenergy should be avoided in the ureter because of thermal side-effects (i.e. hightemperature at the tip of the ultrasound probe).Q. How does electrohydraulic lithotripsy (EHL) work?A. An underwater spark plug is generated by applying voltage/current to two concentricelectrodes with different voltage polarities, which are 1 mm apart andseparated by insulation. This electrically generated spark at the tip of the proberesults in the momentary production of heat in a localised area, and a smallamount of irrigant (which is typically water) surrounding the electrode is vaporised,forming a gas bubble. Subsequent expansion and collapse of the gas bubblegenerates a hydraulic shock wave in 1/800 second, which impacts on the stone.Viva practice for the FRCS(Urol) examination336Collapse of the cavitation bubble can be symmetrical (around 1 mm from stone)or asymmetrical (around 3 mm from stone). The symmetrical aspect results inthe production of a strong secondary shock wave, whereas the asymmetrical partresults in the formation of high-speed microjets. Both of these then result instone breakage in a similar mechanism to ESWL (see above).The probe should be placed on or not more than 1 mm from the stone.EHL is delivered using a flexible probe (via cystoscope) and is generally usedto fragment bladder stones.EHL should never be used in the ureter, as it may result in ureteric perforation.Q. How does ultrasound lithotripsy work?A. Ultrasound waves, produced by an ultrasound generator, are transmitted down a

hollow probe resulting in vibration of the probe tip. This vibration, when in contactwith the stone, produces a drilling or grinding action leading to stone fragmentation.Ultrasound is used in PCNL, often in combination with a lithoclast(as the ultrasound probe is hollow, it is able to suck up small stone fragments). Inaddition, this energy form is used for disintegration of bladder stones. As it is arigid probe it is used with rigid endoscopes only.Ultrasound must not be used in the ureter, as vibration of the tip results in high temperaturesand therefore there is a significant risk of ureteric perforation.Q. How would you ensure laser safety in theatre?A. • Make sure that the theatre doors are closed throughout the procedure.• Ensure that a warning sign is displayed at the theatre entrance doors, andthat a warning light at these doors comes on when the laser is being used.• The theatre that is used should have a non-reflective coating on the walls.• Minimise the number of staff who are present in theatre.• The Laser Safety Officer should be present.• The surgeon and staff handling the laser should have been trained on a certifiedlaser course.• Appropriate eye protection (goggles) should be worn, depending on thewavelength of the laser being used.• Laser should be placed on standby when not in use.• The laser pedal should have a guard.Q. What is the device shown in Figures 14.4a and 14.4b and how does it work?Figure 14.4a Figure 14.4bTechnology in urology, principles of uroradiology and miscellaneous337A. Figure 14.4a shows the generator for the Swiss LithoClast Master.Figure 14.4b shows the foot pedals used to activate the Swiss LithoClastMaster.The Swiss LithoClast Master has both a lithoclast and an ultrasound probeand is used for PCNL. During this procedure the lithoclast is combined with thehollow ultrasound probe, which is able to suck up stone fragments.Principles of uroradiologyQ. What is the machine shown in Figure 14.5 and how does it work?Figure 14.5A. This is an ultrasound machine. It can be used as either a diagnostic or therapeutictool in medicine. High-frequency sound waves are produced by the passageof current through a piezoelectric transducer, and are subsequently focused.Medical ultrasound waves have frequencies in the range 2–18 MHz. Lower frequenciesare used to look at ‘deeper’ tissues, as the attenuation of sound wavesis greater at higher frequencies. For example, a transrectal ultrasound (TRUS)probe works at about 7 MHz, and transabdominal ultrasound works at around3.5 MHz. Ultrasound waves pass into the body via an interface consisting of thesoft rubber coating on the transducer and gel. The sound waves are deflectedback to the transducer, depending on an appropriate density change within theViva practice for the FRCS(Urol) examination338tissues. Large density changes (e.g. fluid and stone) produce a greater ‘echo’, andthe time taken for the waves to come back to the transducer can determine thedepth of the tissue.Q. What are the main therapeutic applications of ultrasound?A. The main current therapeutic applications of ultrasound are lithotripsy (extracorporeal,during percutaneous nephrolithotomy and intracorporeal) and highintensity

focused ultrasound (HIFU), which is used in the treatment of prostatecancer. Ultrasound as a modality can guide other therapies such as prostatebrachytherapy, cryotherapy and extracorporeal shock-wave lithotripsy.Q. A 55-year-old man attends with acute loin pain and dipstick haematuria.His renal function is normal and there are no contraindications to intravenouscontrast administration. What is your radiological investigation ofchoice and why?A. See the chapter on urinary stone disease.Q. A 62-year-old woman presents with possible renal/ureteric colic. She hasnon-insulin-dependent diabetes with a normal serum creatinine level. Thecasualty officer has arranged an IVU which revealed a 6-mm vesico-uretericjunction stone. The patient has been handed over to your care. Whatare the concerns about this management and how would you deal with it?A. See the chapter on urinary stone disease.Q. What are the general contraindications to administration of intravenouscontrast media?A. The contraindications to intravenous contrast media are as follows:• allergy to media• impaired renal function (creatinine concentration > 130 μmol/l)• metformin usage (see chapter on urinary stones)• untreated hyperthyroidism and myelomatosis.Q. A 64-year-old man is referred for an MRI following the diagnosis of prostatecancer. He has previously had intracranial surgery following a stroke,and he works as an electrical engineer. What would be your concerns?A. In this particular case, my concerns would be that the patient may have anintracranial clip (e.g. for an aneurysm), or that he may have an intra-ocular ferrousforeign body (secondary to his job). Imaging should not be performed onpatients with intra-cranial clips unless one is absolutely certain that they are MRIcompatible. Patients who may have metal foreign bodies in their eyes shouldhave radiographs of their orbits performed prior to MRI scanning. Radiographscan pick up objects ≥0.1 mm in size, and ferrous foreign bodies below this sizeare not thought to be dangerous.Other implanted devices that are contraindicated include ICDs, pacemakers,cochlear implants, dental implants, neurostimulators, ocular implants, tissueexpanders and prosthetic heart valves (depending on the type).Extra-cranial surgical clips (e.g. following abdominal surgery) are generallyencased in fibrous tissue, However, they may cause artefact, and scanning shouldbe deferred for 6 weeks post-operatively.Technology in urology, principles of uroradiology and miscellaneous339Q. Briefly describe the physics behind magnetic resonance imaging. What isthe difference between T1 and T2 images?A. Magnetic resonance imaging utilises the nuclei of hydrogen atoms (protons).The protons usually spin in a random fashion, However, on entering the MRIscanner they align with the magnetic field in the longitudinal plane (the magnetin an MRI scanner is always ‘on’!), and produce a secondary spin (precession) atthe same frequency, which will vary according to the strength of the magnet. Aradio-frequency (RF) pulse is applied, which gives the nuclei the energy to moveout of alignment and into the transverse plane, and to precess in phase with oneanother. When this pulse is removed, the atoms release their energy in two ways.First, energy is released back into the surrounding environment, causing magneticmovements to relax and realign back into the longitudinal plane, a processreferred to as T1 relaxation. Secondly, nuclei then lose their precessional coherence

and dephase, due to energy loss between adjacent nuclei, and this process isreferred to as T2 decay. The release of energy is picked up in the transverse planeas an electrical voltage by a receiver coil, and this is the MR signal.T1 relaxation occurs more rapidly in fat, as the size of the molecules enablesthem to return energy to the environment more quickly. This means that thereis a greater degree of transverse magnetisation following the next RF pulse,resulting in a very bright signal from fat on T1 weighted images, whereas fluidremains dark. These scans are excellent for viewing anatomy, due to the goodtissue differentiation.T2 weighted images rely on the process of T2 decay, which occurs moreslowly in water, and therefore maintains transverse magnetisation for longer,resulting in a higher signal. Consequently, water has a very bright signal on theseimages, producing a scan which is more useful for demonstrating pathology.Q. What is nephrogenic systemic fibrosis? How may this be related to MRIinvestigations?A. Nephrogenic systemic fibrosis (NSF) is a condition of unknown cause that affectspatients with renal disease. It causes tightening of the skin of the extremities andsometimes of the trunk. It can be fatal, and 5% of patients develop the fulminantform. Causes of death are related to respiratory complications, clotting abnormalitiesand fractures/falls, among others. There is no consistently successfultreatment for NSF, although various strategies, including steroids, plasmapheresisand renal transplant, have been used.Recent reports have linked the use of gadolinium-containing contrast agentsto the development of NSF in patients with renal impairment. Until furtherinformation is available, gadolinium-containing contrast is used with great cautionin patients with a GFR of < 60 ml/min/1.73 m2, including dialysis patients.The Royal College of Radiologists has recommended that if patients mustreceive these agents, they should be specific ‘highly stable’ agents, and that theuse should not be repeated within 7 days. The smallest dose possible should beused. Specific agents (Omniscan, Magnevist and Optimark) should not be used.Q. You have requested an MAG3 scan on a 29-year-old man whom you suspecthas a PUJ obstruction. What is MAG3, how is it handled by the kidney,and what should the patient know prior to the test?Viva practice for the FRCS(Urol) examination340A. MAG3 stands for mercaptoacetyltriglycine. MAG-3 is attached to the radioactivetracer technetium 99m, an isotope with a short half-life (approximately 6hours) that is used for other nuclear medicine scans, such as DMSA. MAG3 isprincipally excreted by tubular secretion (90%), although approximately 10% isfiltered at the glomerulus. Radioactivity is recorded via a gamma-camera (as withDMSA).The patient will be asked to attend the nuclear medicine unit, and beforethe investigation they will have to empty their bladder. Their usual medicationsshould not be stopped, and the patient should be well hydrated. Childrenshould not be brought along for the scan due to the potential radiation risk. Acannula is inserted, and a diuretic is injected (usually 15 minutes prior to thetest, although protocols vary). The patient does not need to undress, althoughmetal objects should be removed. The patient sits on a chair while the MAG3is injected through the cannula. They then have to sit still for approximately 20minutes while images are recorded. The patient is asked to keep well hydratedafter the test.Please also refer to the chapter on paediatric urology.Q. A 2-year-old girl requires an MAG3 scan to investigate a unilateral hydronephrosis.

The parents are concerned about the process surrounding thescan and the risk of radiation. How would you reassure them?A. Although the investigation is associated with radiation exposure, the overall dose islow (approximately 0.7 mSv). This is equivalent to about 4 months of backgroundradiation. By comparison, air travel (at 26 000 feet) provides approximately 3 μSvper hour at temperate latitudes, and approximately 1 μSv per hour around theequator. Therefore no investigation involving radiation is entirely without risk.However, the benefits of the investigation need to be weighed up against the risks.Children should eat and drink as normal before the scan, and should not stopany regular medications. The child should attend the ward in a well-hydratedstate, and the paediatrician will insert a cannula after the application of anaestheticcream. Occasionally the child may need some sedation. Diuretic may beinjected prior to the isotope injection. The child must lie on a bed for approximately20 minutes. They do not need to be undressed, but will have to removeany metal objects. After the scan they should be kept well hydrated and emptytheir bladder regularly.Please also refer to the chapter on paediatric urology.Q. You have requested a DMSA scan on a 34-year-old woman to look forthe presence of renal scarring suggested on an ultrasound scan. What isDMSA, and how is the scan performed?A. DMSA stands for dimercaptosuccinic acid. It is attached to the radio-tracertechnetium-99m (see above). DMSA is a cortical scanning agent that localises inthe proximal tubule. It is minimally excreted, and its presence is a reflection offunctioning renal tissue and nephrons.An important difference between the ‘patient experience’ of DMSA comparedwith that of MAG3 is that patients may be in the hospital for many hoursduring a DMSA renogram. If a female patient suspects that she may be pregnant,she should inform the department before attending, and should not beTechnology in urology, principles of uroradiology and miscellaneous341accompanied by children. A cannula is inserted into the patient, and the isotopeis then injected. The static images are taken after an interval of approximately2–4 hours post-injection. The patient is not required to undress, but any metalobjects should be removed. During the actual scan they will have to lie still on acouch. The gamma ‘camera’ is placed close to the kidneys but not touching thepatient. After the scan the patient is asked to keep well hydrated and to emptytheir bladder regularly.Q. What steps are necessary to ensure X-ray safety in theatre?A. First, I review the case in question, justifying my use of radiation exposure. Infemale patients of childbearing age a pregnancy test is performed prior to leavingthe ward. In theatre suite, I make sure that the theatre doors are closed throughoutthe procedure. In addition, I ensure that the warning sign is displayed at thetheatre entrance doors, and that a red warning light at these doors comes on whenX-rays are being used. Personal protection, in the form of lead aprons and thyroidshields, is available to all personnel. X-rays are then used according to the ALARA(As Low As Reasonably Achievable) principle. The X-ray source (on the lowerstem of the C-arm) is placed as close to the operating table as possible, in order todecrease radiation scatter. One should attempt to keep a good distance from theradiation source, as radiation exposure is inversely proportional to distance fromthe source. Intermittent screening is preferred to continuous screening. The alarmon the machine sounds when the radiation dose limit is reached.MiscellaneousRenal failure and transplantationQ. Outline the main complications of chronic renal failure.

A. The main complications that affect patients symptomatically are fluid overload,anaemia, renal osteodystrophy, pericarditis anaemia and the effects of cardiovasculardisease. Hypertension, dyslipidaemia and the metabolic complications ofacidosis and hyperkalaemia are factors that can lead to progression of the above.Q. Describe what you see in Figure 14.6. What is the composition of thissolution?Figure 14.6Viva practice for the FRCS(Urol) examination342A. Figure 14.6 shows a dialysate solution. It consists of water, sodium (132–155 mmol/l), potassium (0–4 mmol/l, i.e. sub-physiological concentration), calcium,magnesium, chloride, bicarbonate (or acetate – as a buffer) and glucose.The pH is in the range 7.1–7.3.Q. What is the device shown in Figure 14.7? What are the principal differencesbetween haemodialysis and haemofiltration?Figure 14.7A. This device is a haemodiafiltration (HDF) filter. HDF is a process that combinesdialysis and haemofiltration.Haemodialysis works by two main mechanisms, first and principally the diffusionof solutes across a semi-permeable filter (made of modified cellulose or syntheticmaterial), and secondly the principle of ultrafiltration, which is caused bythe convective flow of solutes and liquids. The negative pressure that is necessaryto allow this to occur is produced via the outlet pump of the dialysis machine.Haemofiltration does not use a dialysate solution, and relies on a hydrostaticpressure gradient alone to produce ultrafiltration. Fluid is replaced either beforeor after filtration. Haemodynamic stability of patients is thought to be bettermaintained by utilising filtration alone rather than diffusion.Q. How may permanent venous access be created, and what are the complications?A. Permanent access is provided principally via either radial or brachial fistulae.The arteries are anastamosed to the cephalic vein. Brachial fistulae are associatedwith a higher risk of ‘steal’ syndrome due to the higher flow rates. Alternatively,the arteries and veins may be linked with a ‘bridging graft.’Common complications include thrombosis of the fistula or graft, stenosis(usually occurring at or distal to the fistula or graft), ischaemia of the digits,infection (of grafts), aneurysm/pseudoaneurysm formation, superior vena cavaobstruction or extravasation into limbs.Q. What are the principles of peritoneal dialysis? What are the different typesof peritoneal dialysis? What complications may occur?A. Peritoneal dialysis uses the peritoneum as the ‘dialysis membrane’, and dialysisfluid is instilled into the peritoneal cavity. Solutes move via diffusion down aTechnology in urology, principles of uroradiology and miscellaneous343concentration gradient, and fluid transfer occurs via osmosis, ‘dragging’ somemolecules with it.There are two main systems of peritoneal dialysis, namely continuous ambulatoryperitoneal dialysis (CAPD) and automated peritoneal dialysis (APD).CAPD originally used glass bottles that had to be disconnected and reconnected.This was superseded by a method that used plastic bags, the disadvantageof this being that the patient had a plastic bag continuously attached to them.Modern methods rely on a ‘two-bag’ system with a ‘Y’ connector. This is associatedwith lower rates of peritonitis and allows the patient to be free from a bagwhile not performing fluid exchanges. Typically patients exchange 2 litres of

solution four times in 24 hours. The solution consists of sodium, potassium, calcium,magnesium, lactate and bicarbonate. The pH is low (approximately 5.5).The tonicity of the fluid is increased by the addition of either dextrose, icodextrin(a glucose polymer produced from the hydrolysis of starch) or amino acids.APD is not dissimilar, but facilitates an automated system whereby fastexchanges can be performed overnight.Access to the peritoneal cavity is via a semi-permanent catheter, such as theTenckhoff catheter. This uses a ‘double-cuff’ method to reduce the likelihood ofinfection. Catheters are placed using the Seldinger technique under local anaesthesia,or placed surgically either by open surgery or laparoscopically.Complications associated with peritoneal dialysis may occur at the time ofinsertion of the catheter, and include visceral injury (to bladder and bowel),haemorrhage, leak or infection. General complications of peritoneal dialysisinclude local infections around the catheter (and ultimately tunnel infection).One of the most serious complications is peritonitis. Although potentiallyfatal, this is often treatable by administering antibiotics intraperitoneally. Anuncommon complication is sclerosing peritonitis, in which the peritoneumbecomes sclerosed and fibrosed. Filtration is greatly affected. The aetiologyis ultimately unknown, but is associated with long-term peritoneal dialysisusage and recurrent infections. An even rarer complication is sclerosingencapsulating peritonitis, which results in bowel obstruction and intestinalfailure.PregnancyQ. Outline the main maternal renal tract changes during pregnancy.A. Pregnancy results in generalised relaxation of smooth muscle (due to the effectsof progesterone), which in addition to mechanical factors such as dextro-rotationof the uterus contributes to the hydronephrosis of pregnancy commencing inweeks 6 to 10. Hydronephrosis is seen particularly on the right, probably due tothe uterine dextro-rotation. By 28 weeks of gestation, 90% of pregnant womenwill have hydronephrosis.Pregnancy is associated with an increase in renal blood flow (up to 75%)and an approximately 50% increase in GFR. Creatinine clearance is thereforeincreased in pregnancy, and this is reflected in relatively reduced levels of serumcreatinine and urea. Proteinuria increases up to 3 g/day, and glycosuria is verycommon.Viva practice for the FRCS(Urol) examination344Q. A 24-year-old woman is referred to you by the obstetricians. The patientis 21 weeks pregnant and has acute left loin to groin pain, a normal serumcreatinine level, and no evidence of sepsis either clinically or biochemically.What imaging modalities are available to you diagnostically?A. Ultrasound is the least invasive investigation, but is not particularly sensitivein the detection of ureteric calculi, and is obviously operator-dependent.Hydronephrosis, as mentioned above, is not a specific marker for obstructionand stones. However, a dilated ureter below the iliac vessels may be more suggestiveof a stone or other obstruction. The presence or absence of ureteric jets mayalso be helpful.IVU is feasible, but carries an inherent risk of radiation exposure, so thismodality is not commonly utilised. However, the absolute risk of a (limited) IVUis low. The contrast medium itself carries no specific risk to the pregnancy.With regard to cross-sectional imaging, CT is avoided due to the relativelyhigh radiation risk. The safety of MRI in pregnancy has not been fully elucidated.However, an experienced radiologist may be able to detect the stone as a

filling defect within the ureter, and this imaging modality is therefore sometimesused.Q. The above patient is found to have a left lower ureteric stone with moderatehydronephrosis on MRI and ultrasound. How should this patient betreated medically?A. There should be close consultation with the obstetric team. In addition, thosewho are unfamiliar with prescribing in pregnancy should refer to the BritishNational Formulary. Simple analgesia such as paracetamol or co-dydramol maybe used, but non-steroidal anti-inflammatory drugs should be avoided (particularlyin the third trimester), due to the risk of premature closure of the patentductus arteriosus in the unborn. Maternal use of opiates such as pethidine andmorphine is associated with respiratory depression in the newborn.Q. What are the options for antibiotic usage in pregnant women with urinarytract infection?A. Again one should refer to the British National Formulary. In general, penicillinsor cephalosporins are safe in the non-allergic patient. Antibiotics that are commonlyused in non-pregnant patients may have adverse effects. Trimethoprim’smechanism of action is to interfere with bacterial dihydrofolate reductase andthe production of folic acid. There is therefore the possibility of teratogenicity,particularly if this drug is used during the first trimester. Quinolones, such asciprofloxacin, are contraindicated in pregnancy due to the risk of arthropathy inthe fetus. Finally, gentamicin has been found to lead to an increased risk of auditoryor vestibular nerve damage during the second and third trimesters.OthersQ. How would you ensure correct site surgery (e.g. in patients undergoingradical inguinal orchidectomy or nephrectomy)?A. I use the pre-operative marking recommendations as set out by the NationalPatient Safety Agency and the Royal College of Surgeons of England.5

Technology in urology, principles of uroradiology and miscellaneous345During consent the correct side should be marked by the operating surgeon.A checklist is attached to the patient notes and then completed sequentiallyby the multi-disciplinary team prior to leaving the ward, on arrival in the theatresuite, in the anaesthetic room, and then finally in the operating theatre immediatelybefore the start of surgery. Each check is only dealt with once the previousone has been completed and signed off.Appropriate radiological investigations must also be available in theatre andbe viewed by the surgeon prior to commencing the surgery.In addition, more recently I have also become aware of the recent WorldHealth Organization Surgical Safety Checklist which is being introduced intomost NHS trusts.Q. What precautions would you take when inserting a prosthesis (e.g. AUS,penile)?A. In my practice, steps to reduce the risk of infection begin prior to the surgicalprocedure itself. The patient is advised to have Hibiscrub (chlorhexidine) washesor showers for 24–48 hours and Naseptin cream. Any other focus of infectionthat is detected pre-operatively is also treated prior to consideration for surgery.At induction of anaesthesia, prophylactic broad-spectrum intravenous antibioticsto cover skin commensals are given. Shaving of the surgical site is performedin theatre prior to surgery. During the procedure itself, I ensure that the lowestnumber of theatre staff possible are present in the operating room, and that theirmovement in and out of theatre is minimised. I ensure meticulous haemostasisat the time of surgery. Antibiotic solutions (e.g. gentamicin) can be applied to

the prosthesis once it has been removed from the sterile packaging, as well asirrigation of the wound with antibiotics prior to placement. When inserting theprosthesis, fresh gloves are applied and a no-touch technique is used. Typically, Iwould use a small swab to handle the prosthesis. After the procedure, antibiotictreatment is continued according to local policy.Q. How would you manage a patient who begins to experience difficultybreathing following scrotal injection of lignocaine, prior to vasectomyunder local anaesthetic?A. This should be treated as an emergency, as the patient is likely to be having ananaphylactic reaction (due to allergy to lignocaine). Initially assess the patientand confirm the diagnosis, and request a nurse or colleague to fast bleep the‘Arrest’ team. While waiting for the emergency team to arrive, follow ALS principlesand check the airway, breathing and circulation. Oxygenate the patientand gain intravenous access.From the resuscitation trolley give 0.5 ml of 1 in 1:1000 adrenaline intramuscularly.Give 200 mg of intravenous hydrocortisone and 10 mg of intravenouschlorpheniramine (Piriton).References1. Tolley D. Ureteric stents, far from ideal. Lancet 2000; 356: 872–3.2. www.valleylab.com/education/poes/index.html3. www.mhra.gov.uk/home/groups/dts-bi/documents/websiteresources/con2023451.pdfViva practice for the FRCS(Urol) examination3464. www.baus.org.uk/information_links/procedure_specific_consent_forms.phtml5. National Patient Safety Agency and Royal College of Surgeons of England.National Patient Safety Alert 06. Joint Commission on Accreditation of HealthcareOrganizations, April 2003; www.npsa.nhs.uk